Proteases play a key role in metabolism and in the pathology of numerous disorders. As a consequence, compounds that specifically inhibit protease activity are often therapeutic. For example, renin is an aspartyl protease that cleaves angiotensinogen to angiotensin I. Angiotensin I is hydrolyzed by angiotensin converting enzyme (ACE) to angiotensin II, which is a potent vasoconstrictor and stimulant of aldosterone secretion. Compounds that inhibit the activity of ACE, such as captopril an orally active ACE inhibitor, are therapeutically effective for treating hypertension and congestive heart failure. Renin inhibitors are thought to have similarly beneficial therapeutic activity.
Activated ketone-based inhibitors have found uses as inhibitors of four different classes of proteases, serine proteases, aspartyl proteases, cysteine proteases and metalloproteases, because they exist as hydrates in aqueous media and directly serve as transition state analogs and/or react with a nucleophilic residue (such as the serine hydroxyl or cysteine sulfhydryl) to form a reversible hemiacetal-type intermediate. For example, phenylalkyl ketones are potent and competitive reversible inhibitors of interleukin 1-.beta. converting enzyme (ICE) and thus, are thought to have therapeutic use for treatment of certain chronic inflammatory disease states. The precursor alcohols for these ketones have been reported to have substantially reduced protease activity compared to the corresponding ketone [see, e.g., Patel et al. (1988) Tetrahed. Lttrs. 29:4665-4668; Patel et al. (1993) J. Med. Chem. 36:24310-2447].
Trifluoromethyl ketones are inhibitors of, for example, human leukocyte elastase (HLE), which is a serine protease. This enzyme has been implicated as a pathogenic agent in a variety of disorders, including pulmonary emphysema, rheumatoid arthritis, adult respiratory distress syndrome (ARDS), glomerulonephritis and cystic fibrosis [see, e.g., Skiles et al. (1992) J. Med. Chem. 35:641-662; Angelastro et al. (1994) J. Med. Chem. 37:4538-4554].
Proteases are also implicated in diseases, such as Alzheimer's Disease (AD), that are characterized by the accumulation of amyloid plaques. Amyloidogenic A.beta. peptides (A.beta.) are the principle component of the amyloid plaques that accumulate intracellularly and extracellularly in the neuritic plaques in the brain in AD. A.beta. is a 4.5 kD protein, about 40-42 amino acids long, that is derived from the C-terminus of amyloid precursor protein (APP). APP is a membrane-spanning glycoprotein that, in the normal processing pathway, is cleaved inside the A.beta. protein to produce .alpha.-sAPP, a secreted form of APP. Formation of .alpha.-sAPP precludes formation of A.beta.. It has been proposed that A.beta. accumulates by virtue of abnormal processing of APP, so that compounds that inhibit the activity of enzymes responsible for A.beta. production are being sought [see, e.g., Wagner et al. Biotech. Report (1994/1995), pp.106-107; and Selkoe (1993) TINS 16:403-409].
Because proteases are implicated in numerous disorders, there is a need to develop potent and specific inhibitors of these enzymes. Therefore, it is an object herein to provide methods of treating disorders in which protease activity plays a pathological role. It is also an object herein to provide protease inhibitors.